Sorry , the Vulcan Death Grip for the E5 , I don't know . But you still can try the Hard Reset : dial *#7370# . This will DELETE all personal data from the device memory . You will need a backup for saving them .
The Hard Reset will not effect the memorycard . When the pictures (and also the thumbnails) are stored on MC , you will have to delete the _PAlbTN folder(s) . These folders contain the thumbnails .
You can use a Cardreader on PC . Set filemanager to UNHIDE to be able to find the _PAlbTN folders , hidden in the Image Folders and/or Video Folders .
Delete the appropiate (or all) _PAlbTN folders manually .
On the device you can do this allso , by installing X-Plore . Set X-Plore to unhide . Search the _PAlbTN folders and delete as you wish .http://www.lonelycatgames.com/?app=xplore
BTW : X-Plore is free (eternal trial) and has a cute built-in Image Viewer .

There is no risk in deleting the _PAlbTN Folders : as soon as you open the Gallery , the device will automatically create new thumbnail folders . This can take a while , though . Depending on the amount of pictures .